Curing coatings

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

It is noteworthy that an important industrial application is based on pure silicone network [9]. This is the organic PSA release technology where an uncured silicone is deposited as a thin coating to a flexible substrate. Strong adhesion develops at the silicone-substrate interface whilst the coating cures. 

Powder epoxies Applied as powder either by electrostatic gun or fluidized bed, these materials must be cured at 200-250°C. The coating cures within a few seconds and is normally water quenched to control cure time. They have good resistance to water but will tend to chalk on outdoor exposure. 

Pigmented Coatings Cured with Visible Light... 

Zinc ferrites are excellent general-purpose pigments of yellowish brown color. As opposed to iron oxide yellows, zinc ferrites offer higher heat stabiUty and can be used in plastics and coatings cured at temperatures above 120 °C. Zinc ferrites are coloristically not as clean as rutile yellows. Zinc ferrites can be sUghdy magnetic. 

During coating, curing, and storage, many pharmaceutical film coatings become sticky and the coated... 

Comparison of Rates of Cure. The rate at which coatings cure is generally based on personal judgment of the time required to become nontacky to the touch. The test is simple and widely used, but it is highly subjective. 

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